Very high stability oscillators are used for numerous purposes and particularly in telecommunications and satellite navigation systems. In order to be able to exploit the signals supplied by such oscillators, it is necessary to have very high performance phase comparators combining a high precision and a wide range. It is currently necessary to obtain a precision of the order of one nanosecond for a range of one millisecond. The range in which this precision is required can exceed 10.sup.7 times the duration of the period of the signal transmitted and the frequencies of these signals currently reach values of 1 to 60 MHz.
The conventionally used comparators are only able to satisfy one of these criteria. Thus, as the two criteria are incompatible, the comparators making it possible to obtain a high precision do not make it possible to simultaneously cover a wide range or, they make it possible to cover a wide measuring range, but with only a very moderate precision.
Moreover, the operating principle of these comparators consists of carrying out modulo 2.pi. measurements. It is therefore necessary to add a frequency divider to meet this requirement, which increases the equipment costs. In addition, this solution leads to measurement noise, greater than the noise produced by the actual oscillators.